The Longitudinal Assessment of Bariatric Surgery (LABS) was conceived to address important issues in bariatric surgery and in disease pathogenesis and pathophysiology in the obese and morbidly obese. LABS explores relationships among patient characteristics, clinical conditions and co-morbidities, serologic and genetic markers, surgical procedures and other aspects of care, with clinical, psychosocial and health economic outcomes. LABS' primary achievements in its first 5 years have been to define the domains of exploration, identify appropriate metrics, and design and implement two major and several more restricted protocols. By 12/31/2007 LABS had completed enrollment and initial surgery in a cohort of 4,772 obese patients (median BMI 46.5) to study short-term safety of bariatric surgery (LABS-1), and as of October 13, 2008 had enrolled and completed surgery in 1,991 of the planned 2,400 person cohort in whom longer-term safety and efficacy will be studied (LABS-2). These studies employ the rigorous research infrastructure the LABS has built at 6 Clinical Centers representing diverse care delivery systems and patient populations. LABS patients are enrolled at 6 academic & 4 affiliated community hospitals, undergoing operations by 33 surgeons. The result is a unique LABS-2 cohort with heterogeneous patient characteristics undergoing a diversity of surgical procedures. LABS is now seeking funding for a 5 year extension to enable it to address scientifically important research questions from the LABS-2 study that cannot be addressed with the limited follow-up currently supported. This extension would permit LABS to evaluate the durability of weight loss and comorbidity improvement, as well increasingly recognized late-emerging effects of surgery such as hypoglycemia and suicide, and effects that change over time. The critical scientific advantages of the multi- center LABS consortium include heterogeneity of the participant base, the ability to recruit a large number of patients in important sub-groups, and an existing research infrastructure with rigorous data collection practices, high levels of data accuracy and completeness, rigorous follow-up, and a comprehensive database of cleariy defined data elements to address these important issues. RELEVANCE (See instructions): The obesity epidemic has profound health issues, e.g. -300,000 deaths/year, a reduction in life expectancy, and enormous costs. Bariatric surgery seems the most reliable means to major weight loss and correction of co-morbidities (e.g. type 2 diabetes). While its safety & long-term benefit remain uncertain, ~250,000 annual operations are expected. This proposal seeks to extend LABS studies that will answer many of these issues.